A persistent issue for nanocomposites, and in turn composites that contain nanoparticles, is cost, including cost associated with the processing steps. One approach to processing nanocomposites is a solvent-based approach where an aqueous dispersion of nanoparticles is the raw material. The dispersion is typically dilute, in which the nanoparticles are present in an amount between about 15-40 weight percent. A solvent, typically a water-miscible solvent, is added in a 1:1 ratio with the water in the dispersion, further diluting the nanoparticles. The solvent is typically chosen so that the dispersed state of the nanoparticles is maintained. The solvent further serves to counteract the thickening effect of silica nanoparticles on resin systems. A surface treating agent is typically used to make the nanoparticles more compatible with the matrix resin. The surface treating agent is typically soluble in the water:solvent:nanoparticle dispersion. After completion of the surface treatment process, the modified nanoparticle dispersion is mixed with resin. This is followed by removal of the water and solvent to yield a nanocomposite.
There is a cost associated with the processes of preparing the nanoparticle aqueous dispersion, addition of solvent, surface treatment of the nanoparticles, compounding the nanoparticles into a resin, and removal of the water and solvent to form the nanocomposite. The removal of water and solvent is typically the most expensive of these processes.
Another approach to processing nanocomposites is the solvent-free approach where dry, aggregated particles are reduced in size, surface treated, and compounded into a resin by a mechanical grinding process (e.g., milling) without the aid of a solvent.